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Intimately Bonded

They can be found in modern aircraft, racing cars and yachts - and have even flown to the moon. We’re talking about composites – extremely strong, lightweight construction materials. With their outstanding properties, they are the materials of the future.

Composites are up to 70 percent lighter than steel and 30 percent lighter than aluminum - but at the same time are extremely strong and corrosion resistant. This combination makes them interesting in a great many sectors. Thanks to weight savings, they reduce the fuel consumption of aircraft and cars. In the tour de France, composites are ahead of the pack in ultra-lightweight racing bikes. And mobility-impaired people welcome lightweight and maneuverable wheelchairs.

Strong Connections

Composites – also known as fiber-reinforced materials – are special plastics in which polymers are combined with reinforcing carbon, glass or mineral fibers. For the production of thermoset composites, unsaturated polyesters (UP), vinyl esters (VE), phenolics, epoxy resins (EP), melamine resins and polyurethanes (PU) are principally used.

The combination of thermosets and reinforcing fibers is responsible for composites’ outstanding properties

  • light weight
  • high mechanical stability
  • high fatigue resistance
  • very high corrosion resistance
  • very good impact strength
  • high design flexibility
  • very good acoustic properties combined with high stiffness

Many Roads Lead to the Goal

There are many different methods used for the production of fiber composites. The best process for the job is chosen depending on the application and requirements.

SMC Method (Sheet Molding Compound)

In this process, sheet-like SMC resin mats are produced from a high-viscosity fiber-resin composite. When the fiber/resin compound is processed in a closed mold under heat and pressure, its viscosity decreases. That allows the resin and the fibers it contains to flow in the mold. The thermoset then cures within the closed mold.

Applications: e.g., automotive engineering, electrical parts and construction

BMC Method (Bulk Molding Compound)

BMC is a pasty mass, which is processed by reaction injection molding. The BMC part can be produced as soon as the BMC compound has been kneaded. The main difference from SMC lies in the fiber content and fiber length.

Fields of application: for example transport, electrical parts and construction

RTM Method (Resin Transfer Molding)

In the RTM process (resin injection molding) dry fibers, mats or scrims are laid in a mold. After the mold is closed, liquid resin is injected. It fills all the cavities in the press mold and impregnates the reinforcing material. The part is typically heat cured.

Applications: e.g., parts requiring a class A surface


In the pultrusion of thermosets, the reinforcing fibers are impregnated by passing them through a resin bath. The resin-impregnated fiber strand is then brought to the near net shape at a number of preform stations and shaped and cured in a heated mold.

Hand Layup

Hand lay-up is the best known processing technique. Dry fiber mats or scrims are laid in a single-shell, open mold. More resin is introduced and rolled out by hand rolling: resin is forced through the reinforcing material by rolling, thus removing air and completely impregnating the reinforcement.

Applications: large-format and complex components, ideal for prototypes and small series

Fiber Spray-Up

In this process, the glass-fiber rovings are chopped to predetermined lengths in a chopping machine. The chopped glass is combined with the resin in a spray gun and applied to an open mold. It is then compacted and deaerated with a roll by hand before curing.

Applications: production of boat parts or amplification cells of acrylate

Infusion and Prepreg Method

A dry fiber material is draped over a mold coated with release agent. The fiber material is covered with peel ply and a resin distribution mesh that helps the resin to flow more evenly. In a next step, the mold is sealed with a vacuum film. After the vacuum is generated, the liquid resin is injected into the mold.
The only difference between this and the prepreg method is that the latter uses fabric pre-impregnated with resin.

Applications: e.g., for manufacturing small series and prototypes

Four Product Groups, One Aim: High-Quality Composites

As a leading supplier of composites components, WACKER helps ensure that fiber composites can be produced in ever better quality. WACKER as a partner will allow you to access all these products from a single source.

Find out more about composite ingredients from WACKER

WACKER supplies products for manufacturing fiber composites in ever higher quality. Profit from WACKER’s one-stop solutions and expertise. Visit our product section for more details.

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